In this project we propose to analyze several recurring or unique chromosomal abnormalities, from T-cell leukemia derived cell lines or from leukemic primary cells, that involve the T-cell receptor a-chain gene (TCRA). This analysis will involve the determination of the breakpoint junction structure, as well as the study of the expression of the genes surrounding the breakpoints. Specifically, we plan to study two t(8;14) (q24;q11) and a t(11;14) (p15;q11) from different T-cell leukemia cell lines, three inv(14) (q11;q32) and two translocations, with one breakpoint at 14q11, present in the primary leukemic cell from different T-cell leukemia patients. Using in situ chromosomal hybridization and Southern blot analysis, we have determined that the breakpoints of the t(8;14) (q24;q11) occur within the TCRA gene, and in the 3' flanking region of the MYC gene. Using genomic clone libraries in phage gamma vectors, we have isolated the breakpoint junction sequences from both translocations. We will complete this analysis by cloning the reciprocal junctions, sequencing the regions around all breakpoints, and studying the expression of the translocated MYC gene at the transcriptional level. Using similar strategies we will analyze the other chromosomal abnormalities mentioned above. In these studies we will use the new techniques of field inversion gel electrophoresis in order to detect restriction site rearrangements with the large V alpha and J alpha regions of the TCRA gene. The objectives of these studies are: a) to understand the mechanisms involved in the origin of these chromosome rearrangements, b) to identify new genes involved in the rearrangements, and c) to determine the role of these genes and the TCRA gene in the oncogenic process. The information obtained from these studies will be relevant to the understanding of the biology of lymphoid neoplasia, and to its prevention and diagnosis.